For the construction of the Gotthard Base Tunnel in Switzerland, which, with 57 km, is one of the longest tunnels in the world, a ventilation system is required to continue work underground after the shell construction has been completed. It supplies workers and machines with fresh air during the construction work involving track laying, catenary, signalling, etc.
To ventilate a stretch of currently about 25 km, two fans have been installed in cross galleries between the two tunnels in order to ensure a so-called forced-air circulation. These fans have a capacity of 560 kW, a double stage design, a blade diameter of 1.8 m and, at a pressure of approx. 5000 Pa, they have an air flow output of 100 m³/s. The fans achieve these operational values in both operating directions.
Both fans operate in parallel and are equipped with fully automatic control valves and a remote control system to the control centre Biasca.
Due to the installation in the very narrow cross-galleries, the airflow velocity can reach up to 32 m/s. This causes high turbulences and vibrations that affect the entire system.
In order to protect not only the fan station but also the entire system in the cross-galleries, vibration sensors and monitoring instruments such as the VIBROCONTROL 1500 were integrated so as to ensure that problems are detected as soon as possible. When commissioning the system, the software used to configure the monitoring devices and check the start-up values was of great assistance and helped reduce the time leading up to the handover of the operational station.
The company Korfmann Lufttechnik is already looking forward to starting the next project in Sol-Iletsk, Russia, which will involve fans with a diameter of 2.8 m and vibration monitoring provided by their "vibration colleagues" Brüel & Kjaer Vibro which will enable them to provide direct support to their customer in the event of vibration problems.
(Field experience supplied by: Jens Kegenhof, KORFMANN LUFTTECHNIK GMBH)